Expansion Bus I/O Port Operation
8-12
Figure 8–6. Example of the Expansion Bus Interface to Two 16-Bit FIFOs
XA[2]
XRE
XCE
XD[31:0]
XOE
XFCLK
CLK
D[15:0]
OE
FIFO #2
REN
WEN
XD[31:0]
XD[31:16]
XD[15:0]
FIFO #1
REN
WEN
D[15:0]
OE
CLK
Table 8–7. Addressing Scheme – Case When the Expansion Bus is Interfaced to Two
16-Bit FIFOs
Logical Address
A[31:6]
A5
A4
A3
A2
A1
A0
FIFO #1 Address
X
X
X
X
0
0
0
FIFO #2 Address
X
X
X
X
1
1
0
Physical Address
XA5
XA4
XA3
XA2
8.4.1
Asynchronous Mode
The asynchronous cycles of the expansion bus are identical to the
asynchronous cycles provided by the EMIF. During asynchronous peripheral
accesses, XRDY acts as an active-high ready input and XBE[3:0]/XA[5:2]
operate as address signals XA[5:2]. The remaining asynchronous peripheral
signals operate exactly like their EMIF counterpart. For a complete
description, see the External Memory Interface section. The following
minimum values apply to the asynchronous parameters:
-
SETUP
+
HOLD
≥
3
J
SETUP
≥
1
J
STROBE
≥
1
-
If XRDY used to extend STROBE then HOLD
≥
2.